1. Field of the Invention
The invention relates generally to methods and apparatus for turning flat articles and is particularly related to methods and apparatus used for turning envelopes.
2. Description of the Related Art
Turning devices for flat articles that are conveyed horizontally are required in mail processing machines. Examples of flat articles are envelopes, letters, postcards, endless forms issued by a computer controlled printing device that are cut into sheets from an endless web and the like. For example, in an inserter and mail processing machine, sheets are fed one by one, or collected together, to a folding station and subsequently, with or without additional enclosures, are conveyed to an inserting station where the sheets are inserted into an envelope.
After insertion of the sheets into the envelope, the stuffed envelope is forwarded to a postage station where postage is imprinted thereon by a postage meter. In certain inserters, it is necessary to turn the stuffed envelopes either through a 90.degree. or 180.degree. angle. The first case is required if the direction of travel by envelopes through the postage meter is the same as the direction of discharge from the inserting station and the second case is required if the postage meter is connected to the inserting station at a 90.degree. angle relative to the direction of discharge.
In a known device of this kind, as described in U.S. Pat. No. 2,746,221, the envelopes are transferred with their length perpendicular to the direction of travel through the inserting station and received by a rotatable turntable device. The device is driven by the main motor of the inserter through a gear in such a manner that movable gripping arms are provided in the clamping device which engage the envelope to clamp it on the rotatable table of the turning device and retain it until the envelope has been turned 180.degree. by rotation of the turntable. Thereafter, the envelope is received by the postage station, which is located at a 90.degree. angle relative to the direction of travel of the inserting station, and fed to the postage station. In this device, however, the gripping arms, which are controlled by a cam disc, cause a predetermined spring force to be applied to the envelope on the rotatable turntable during its angular rotation so that there exist different pressing forces upon envelopes of different thicknesses.
Additionally, a relatively high noise level is occasioned by the cam disc for controlling the gripping arms as well as the Geneva motion required for driving the turntable. Particularly, lowering of the arms creates noise. Further yet, because the components suffer relatively high wear, the wear on the gripping arms may result in envelopes no longer being securely clamped, particularly at high processing speeds.
To solve the aforementioned problems, the assignee of the instant invention has disclosed a turning device with a modified clamping mechanism, for turning flat articles through a preselected angle, in copending application Ser. No. 718,327 filed on Apr. 1, 1985, entitled "DEVICE FOR TURNING FLAT ARTICLES", in the name of Karl-Heinz Abels, which is hereby incorporated by reference.
The apparatus disclosed in the incorporated application includes a clamping device having two coaxially aligned discs which are coupled to rotate in unison and are axially movable towards one another. The articles to be turned are inserted between the two discs and can be discharged at a predetermined angular position. The clamping device is provided with a driving mechanism by which the discs can be moved between axially spaced apart positions. When a predetermined pressing force is attained upon an article being retained by the discs, the discs can be locked in position during the angular rotation of the turntable unit in order to maintain a constant pressure on the articles being turned. Still, the object to be turned must first be gripped by the clamping device, i.e., be locked for a period of time between the retaining discs and then be released at the appropriate time after the article has been turned through the predetermined angle. Other known types of turning devices are typified by Daily in U.S. Pat. No. 3,758,104, issued Sept. 11, 1973, entitled "TURNING APPARATUS", which instead of using a clamp comprised of 2 discs to grab and release an article, uses a conveyor and means forming two nips generally transverse to the conveyor to turn an article. According to Daily, an inward disc is mounted on a shaft above the conveyor and is free-wheeling with respect to the shaft in order to form a first article engaging nip with the conveyor. An outward disc is secured to the shaft and forms a second article engaging nip with a third disc freely mounted beneath the outward disc on a shaft which drives an end roll of the conveyor. The outward disc is driven at a speed greater than that attained by the inward disc by virtue of its engagement with the conveyor or a moving article thereon.
When, for example, an envelope is conveyed toward the discs, a portion is caught in the nip formed by the outward disc and the third disc. This portion of the envelope is accelerated while the portion of the envelope between the conveyor and the freewheeling disc remains at conveyor velocity. The envelope is thus turned about that area between the conveyor and the freewheeling disc and is discharged from the conveyor to further apparatus such as a postage meter device. The apparatus disclosed in the Daily Patent although providing means to turn an article without using the prior art clamping arrangement, does not accommodate turning articles 180.degree., requires two discs for the 90.degree. turn alone, and requires a conveyor belt between the rotating discs to turn the article. The conveyor belt as a part of the turning device apparatus introduces a separate maintenance and operating element and will be seen to be an unnecessary element to provide 90.degree. and 180.degree. turning capabilities in a turning device. The prior art also encompasses article turning devices, typified by Crawford in U.S. Pat. No. 4,085,839, which do not require rotating discs or clamps. In the Crawford Patent a conveyor belt is again required, but this time is used with side belts for grasping an article to achieve a 90.degree. rotation. Still further, Bashford et al, in U.S. Pat. No. 4,448,407, issued May 15, 1984, and Bashford in U.S. Pat. No. 4,506,878, issued Mar. 26, 1985, teach sheet moving apparatus comprising a combination of a rotatable member, such as a disc, and a movable or pivotal member, including an engaging roller, to change the track in which a document is being conveyed. The Baskford apparatus requires movement of the pivotal member and engagement of one or more rollers with the rotating turntable in order to change the track of an article. In addition to all these moving parts, Bashford does not accommodate applications where the article needs to be turned 180.degree..
In addition to all of the aforementioned problems related to moving parts, noise and wear, the known prior art equipment is bulky, costly and not safe to operate, particularly in view of the number of high-speed moving parts exposed to the operator. It has been determined that it would be advantageous to have an article turning device not requiring a conveyor mechanism to perform the turning per se. In this way the device could be made modular; i.e., could be married to a variety of devices which deliver and/or receive the articles by any known means, e.g., conveyor; injection, etc. Still further, it has been determined that it would be advantageous to have a turning device, with few moving parts, that is a device that is easy to maintain, quiet, and capable of selectively rotating articles through 90.degree. or 180.degree.. This would be particularly useful in the aforementioned inserter and mailing machine combinations where the position of the mailing machine determines how far the envelopes need to be turned. Further yet, it would be advantageous to have a turning device which is inherently safe to operate. To address these objectives the assignee of the instant invention has disclosed flat article turning methods and apparatus in copending application Ser. No. 2,487 filed on Jan. 12, 1987, entitled "Methods and Apparatus For Turning Flat Articles" in the name of Samuel W. Martin now U.S. Pat. No. 4,724,945, which is hereby incorporated by reference. These methods and apparatus are operative in a first mode to take as input a stream of articles delivered along a first path, turn each article 180.degree. and then urge the articles to continue along a second path at a right angle to the first path. These methods and apparatus are also operative in a second mode to take the input stream of articles, turn each article 90.degree. and then urge the articles to continue along the first path. The apparatus disclosed in said Martin copending application includes a substantially flat surface for receiving said articles and means for guiding the articles to the nip of a first, fixed position, pair of rollers. The rollers grab a given article and urge it to pivot 90.degree. about a fixed stop. A second fixed position pair of rollers is used when a 180.degree. pivot is desired. In either case no turntables are used to rotate an article. The surface on which articles are received does not rotate, only the roller pairs rotate. It has proven desirable in some applications to substantially retain the benefits realized by the methods and apparatus disclosed in the Martin copending application and at the same time minimize both the number of rollers which come in contact with the envelopes being turned. Again, the context for operating the desired alternative is on a substantially flat stationary surface as opposed to the prior art devices, such as the devices taught in the referenced Bashford patents, that operate with rollers coming in contact with turntable type rotating surfaces.